Annals of botany最新文献

Background and aims: Many plant species undergo long-distance dispersal through migratory waterbirds. However, there is little information about the effectiveness of this dispersal, especially regarding the chances of plant establishment and the impact of gut passage or the faecal matrix on plant germination, growth and reproductive investment in seeds.

Methods: In a greenhouse experiment, we addressed these questions using an annual mudflat species, Juncus bufonius (Juncaceae), and a perennial emergent aquatic species, Eleocharis palustris (Cyperaceae), whose seeds are dispersed by many waterbird species in Europe. We planted seeds directly in soil or within mallard faeces placed on soil, using both control seeds and seeds that survived gut passage through mallards. Over the following 11 weeks, we quantified germination and plant performance.

Key results: Gut passage reduced germination time of J. bufonius when there was no faecal matrix, and it increased asymptotic height of E. palustris. Presence of the faecal matrix hindered germinability, plant growth and final biomass for both species, along with total seed production for J. bufonius. Presence of the faecal matrix slowed down germination in E. palustris, but had the opposite effect for J. bufonius. It was also associated with greater relative investment in seeds in J. bufonius (more seeds per unit biomass), probably as a consequence of later germination. In both species, earlier germination increased final biomass (and seed production in J. bufonius).

Conclusions: Our results support the importance of waterbird endozoochory in plant dispersal but suggest that it might be more effective when faeces disintegrate, such as when egested into water or disaggregated on land (e.g. by insects). Previous studies with other plants have recorded accelerated germination following waterbird gut passage, and our results show that this can benefit plant fitness.

Background and aims: Ecological niche differentiation is well associated with intraspecific divergence of functional traits, which may lead to the evolution of premating reproductive isolation. However, the link between the ecological niches, trait divergence and premating isolation remains poorly understood. This is particularly pertinent in hyperdiverse areas, such as the Cape Floristic Region of South Africa, where fine-scale ecological heterogeneity has been hypothesized as a major driver of speciation. Using the polymorphic geophyte Gladiolus carneus, endemic to the Cape Floristic Region, we test whether ecological niche differentiation mediates premating reproductive isolation.

Methods: We first tested whether putative ecotypes of G. carneus were distinct based on their floral and vegetative morphology. Next, we documented the abiotic niche, flowering phenology and pollination niche of each putative ecotype and tested whether any resulting niche differentiation causes premating reproductive isolation.

Key results: Seven distinct ecotypes were identified. Using niche modelling and multivariate analyses, we found that these ecotypes occupied distinct abiotic niches, resulting in strong ecogeographic isolation. They also had distinct flowering times, causing varying strengths of phenological isolation. For the pollinator niche, we found that all sampled populations were pollinated by one of three highly effective functional pollinators; however, at the ecotypic level there were no consistent trends, leading to varying strengths in pollinator-mediated isolation. Across all ecotypes, ecogeographic isolation was the strongest barrier to gene flow, which, combined with phenological and pollinator-mediated isolation, caused near complete premating reproductive isolation.

Conclusions: These results suggest that ecological niche differentiation between G. carneus ecotypes might be contributing to incipient speciation within the species complex and further suggest that ecological niche differentiation may be a major driver of speciation in the hyperdiverse Cape Floristic Region.

Background and aims: Leaf abscission is the process whereby plants actively shed leaves through physical detachment at the abscission zone (AZ). Leaf abscission is generally preceded by senescence, during which there is an active reclamation of leaf nutrients. The physiological regulation of leaf abscission remains poorly studied in trees, with a suite of environmental and endogenous signals believed to regulate the process. Here, we sought to characterize the role of water status, leaf gas exchange, senescence, and the phytohormone abscisic acid (ABA) in regulating leaf abscission in temperate trees.

Methods: We developed a novel method to quantify AZ competency (AZC) and simultaneously measured leaf gas exchange, chlorophyll content, water potential, AZC, and ABA levels from late summer until leaf death in four temperate tree species representing deciduous, brevi-deciduous, and marcescent leaf habits. We tested for associations between changes in key physiological traits and AZC in all species.

Key results: The two deciduous species showed contrasting physiological patterns leading to leaf abscission: one species degraded chlorophyll and ceased photosynthesis before complete AZC, while the other retained chlorophyll and continued photosynthesis until complete AZC. The brevi-deciduous species degraded most chlorophyll but developed AZC gradually over a longer period. The marcescent species' leaves fully senesced but did not develop AZC.

Conclusions: These findings demonstrate that leaf senescence and abscission are distinct and variably timed processes across temperate tree species. These results have implications for predicting future leaf lifespan as the climate changes, with the characterization of physiological diversity in the regulation of leaf abscission profoundly understudied.

Background and aims: Petunia provides a valuable opportunity to study speciation in a biodiversity hotspot, focusing on species with varied floral syndromes. Here, we examined a population displaying a range of flower colors, from light to dark purple, to determine its origin and explore the diversification patterns of Petunia.

Methods: We employed Genotyping-by-Sequencing on multiple individuals from different species to assess population structure and hybridization patterns, thereby revealing insights into the evolutionary history of unusual Petunia populations through various demographic models.

Key results: Population structure analyses revealed a distinct genetic component unique to the atypical individuals, with no evidence supporting interspecific hybrid origins. Demographic models and species delimitation methods produced conflicting results, likely due to the rapid diversification within the genus Petunia.

Conclusions: Our findings indicate that tracing the evolutionary origins of Petunia species in a biodiversity hotspot is challenging; however, it offers a valuable opportunity to study speciation in the Neotropics and flower color evolution at both the species and population levels.

Background and aims: The temperate montane coniferous forests in Northeast Asia are among the ecosystems most sensitive to ongoing global warming. However, the timing, patterns, and environmental controls of wood formation in dominant tree species remain poorly understood.

Methods: In this study, we investigated the intra-annual wood formation of Larix olgensis A. Herry along a 750-1450 m elevational gradient in Changbai Mountain, Northeast China, using weekly microcoring and high-resolution climatic data. Environmental drivers of growth onset, peak, and cessation were identified using multiple linear regression models, and the relative contributions of climatic variables to seasonal radial growth were quantified using linear mixed-effects models.

Key results: We found that for every 100 m increase in elevation, the onset of wood formation was delayed by approximately 3.3 days, and the growing season was shortened by around 3.5 days. Growth onset was primarily predicted by photoperiod and growing degree days (GDD), while peak growth was jointly influenced by photoperiod and precipitation. Growth cessation was strongly predicted by photoperiod, with additional contributions from cold degree days (CDD) and seasonal precipitation. Weekly radial growth was best explained by photoperiod and temperature, with vapor pressure deficit showing a weak but significant positive effect, and soil water content exhibiting negative relationship with growth.

Conclusions: These findings demonstrate that photoperiod consistently regulates both the timing and seasonal patterns of wood formation in L. olgensis, while GDD and CDD played distinct and significant roles in predicting the onset and cessation of secondary growth in spring and autumn, respectively. This study provides valuable insight into the phase-specific climatic controls on wood formation and offers a basis for predicting the response of temperate coniferous forests to future climate change.

Background and aims: Soils are reservoirs of key nutrients and enzymes for plant fitness and ecosystem productivity. Epichloë fungal endophytes are well-known to shape plant performance, yet the mechanistic link between Epichloë-mediated changes on plant root genes and root exudates with soil biochemistry is not entirely clear. We studied the effect of the foliar endophyte of grasses Epichloë gansuensis (C.J. Li & Nan) on the soil biochemistry and composition/abundance of host root genes and exudates. We hypothesized that Epichloë would affect soil biochemistry, and that these changes would be associated with endophyte-mediated alterations in root genes and exudates.

Methods: Soil samples, root tissues, and root exudates were harvested from field plots of Achnatherum inebrians (Hance) Keng plants with and without E. gansuensis endophytes. We measured concentrations/activities of nutrients/enzymes in bulk and rhizosphere soils, together with the composition and expression of root genes and exudates that were determined via high resolution LC-MS and RNA-Seq.

Key results: Epichloë altered concentrations/activities of several nutrients/enzymes in both soil compartments (e.g., organic carbon, β-glucosidase), with larger effects in the rhizosphere soil than bulk soil. Epichloë also modified the expression of root genes (e.g., AHCY) and exudates (e.g., malate, ethylene), with several of the changes in root exudates aligned with the altered expression of root genes (e.g., high malate abundance was associated with enhanced expression of their biosynthesis genes). Many of the Epichloë-derived changes in soil nutrients and enzymes levels were functionally associated with the host plant release of bioactive root exudates affected by the endophyte.

Conclusions: Foliar Epichloë endophytes can shape soil biochemistry, root gene expression, and root exudate abundance, and the existence of functional links between soil biochemistry and root exudates in plant-endophyte associations.

Background and aims: Desert and alpine environments, though ecologically distinct, often share similar environmental stressors such as drought and high radiation. Various plant lineages traverse both biomes, which is often associated with transitions in life history strategy, where annuality is more often associated with drier desert habitats and perenniality more common in higher elevations. One such lineage is Cistantheae (Montiaceae), a morphologically diverse herbaceous clade in western North and South America. We aimed to infer a robust phylogeny of the clade as a foundation for taxonomic and comparative work.

Methods: We used double-digest RADSeq to generate reduced-representation genomic data from over 160 samples representing 48 putative species in Cistantheae. Maximum likelihood and coalescent-based phylogenetic methods were utilized to infer evolutionary relationships across the full clade and within major subclades. We tested for signatures of admixture and introgressive gene flow, and reconstructed ancestral life history and climate niche to identify patterns of correlated evolution.

Key results: We inferred a well-resolved phylogeny of Cistantheae, providing strong support for relationships among subclades within Cistantheae. While many species relationships were clarified, we also found evidence of rampant gene flow and incomplete lineage sorting, particularly within the annual Cistanthe clade from the Atacama Desert. Life history is evolutionarily labile across the clade and was strongly correlated with temperature and precipitation-related bioclimatic variables: annuals tend to occur in hotter, drier environments, while perennials in cooler and wetter habitats. Elevational range was also evolutionarily labile, with several species occupying broad elevational gradients.

Conclusions: We present the first densely sampled phylogenomic analysis of Cistantheae, providing key insights into species relationships in the clade. Repeated transitions in life history and climate niche, alongside wide elevational ranges, suggest that many Cistantheae species may be preadapted to both arid and montane habitats. This phylogeny will underpin further comparative, taxonomic, and phylogenomic studies in this ecologically important lineage.

Background and aims: Growth patterns in tropical savanna woody plants remain poorly understood across their vast diversity of strategies and plant forms. Something still little known is whether tropical woody species exhibit rhythmic or seasonal growth. This study investigates growth rhythmicity in Cerrado woody species, focusing on their post-fire resprouting patterns and their relationship with rainfall seasonality and fire.

Methods: We analyzed the number and characteristics of growth units produced after fire events (2020 and 2021 wildfires) in 21 Cerrado species. Satellite imagery and morphological markers along stems - such as internode length and bud scars - were used to assess growth cycles.

Key results: Cerrado species exhibited clear annual growth, typically producing one growth unit per year, closely aligned with the rainy season. Morphological traits reliably marked these cycles. Primary growth was consistently greater in the first growth unit produced after fire, likely due to increased carbohydrate allocation and reduced apical dominance of previous existing stems. This enhanced growth may help position foliage above future flame zones, improving survival. As species exhibited an annual growth pattern, we observed synchrony between the number of growth units and the number of years since the last fire.

Conclusions: Woody plants in the Cerrado grow through annual growth units formed from buds with preformed structures that elongate during the rainy season. The extent of this growth varies among species and individual life histories. Fire, a frequent disturbance, stimulates the production of larger growth units. This response indicates that woody plants can rapidly rebuild aboveground biomass after burning, likely supported by stored carbohydrates and the release of apical dominance. These patterns highlight the resilience of Cerrado vegetation. To deepen our understanding of tropical plant development, future work should relate growth units to species phenology, rainfall variability, and vegetation types.

Background and aims: Knowledge on seed persistence is vital from both theoretical and practical considerations but directly collecting persistence data for many species is unfeasible. Therefore, there is a need to identify traits associated with seed persistence, but studies about the effects of seed size and shape on persistence yielded results varying across regions. We studied 392 species of the Pannonian flora (Central Europe) to asses (i) how seed mass and shape are related to seed persistence, (ii) whether this relationship is consistent across plant functional groups, and (iii) whether seed mass and shape are correlated in different functional groups?

Methods: We collected data on the seed mass and persistence of species and performed measurements to calculate their Seed Shape Index, with higher values indicating greater deviation from sphericity. To account for phylogenetic non-independence, we analysed how seed mass and Seed Shape Index affect persistence in all herbaceous species and separately in four plant functional groups using phylogenetic logistic regressions. To test how seed mass and shape are related to each other in these groups, we applied PGLS regression.

Key results: Across all species, both seed mass and Seed Shape Index were negatively related to persistence, with seed mass having a stronger association. The same relationship was observed in forbs and short-lived species, but only seed shape was related to persistence in graminoid species. The relationship between seed mass and seed shape also varied between functional groups.

Conclusions: Consistent with many studies in other floras, both seed mass and shape were negatively related to persistence in the Pannonian flora after accounting for phylogeny. However, only seed shape was associated with persistence in graminoid species, suggesting that different factors may be at play in forbs and graminoids. Therefore, future studies of this relationship may need to treat and analyse graminoids separately.

Background and objectives: The hyperarid-semiarid gradient of the western Andes, from the coastal Atacama Desert to central Mediterranean Chile, hosts exceptional plant endemism driven by paleoclimatic oscillations, rugged topography, and long-term isolation. Here, we use the columnar cactus genus Leucostele as a model to (1) quantify the influence of geographic isolation and topographic heterogeneity on genome-wide divergence, and (2) test whether zones of secondary contact foster genetic admixture.

Methods: We genotyped 151 individuals from 20 populations of Leucostele using 9,397 SNPs to assess spatial genetic structure, isolation by distance, and the influence of terrain ruggedness and geographic isolation on admixture.

Key results: Spatial ancestry analyses delineated ten latitudinal genetic clusters, with eight populations exhibiting > 75 % ancestry assignment to a single cluster and twelve showing varying degrees of admixture. Genetic differentiation increased with geographic distance, revealing strong isolation by distance across Atacama Desert to southern central Chile. Admixture, quantified as Shannon entropy, varied among populations and decreased significantly with both increasing terrain ruggedness and greater geographic isolation.

Conclusions: Our study reveals that rugged topography and spatial isolation promote genomic divergence by limiting gene flow and fostering distinct genetic clusters while less rugged terrain facilitates secondary contact and admixture, showing that these barriers remain permeable and reproductive isolation is incomplete. This dual influence of topographic heterogeneity underpins the dynamic evolutionary mosaic observed across the coastal Atacama Desert-central Chile gradient.